Isolamento e caracterização de bactérias epifíticas e endofíticas isoladas de Bromélias do gênero Tillandsia

Abstract

The Bromeliaceae family is native to neotropical regions and includes a wide variety of genera and species, being highly adapted due to the presence of foliar trichomes, structures essential for the absorption of water and nutrients. The genus Tillandsia contains the largest number of species within the family and is completely epiphytic, exhibiting a pattern of interaction with microorganisms that is crucial for protection, plant growth, and nutrition, especially regarding nitrogen fixation and phosphate solubilization. Thus, the importance of bacterial communities in Tillandsia species represents a broad research field focused on microbial diversity in Brazilian bromeliads, which has so far been largely neglected. This study aimed to isolate and characterize endophytic and epiphytic bacteria found in Tillandsia species from southeastern Brazil, given the scarcity of studies focused on these interactions and their potential biotechnological applications. For this purpose, samples of Tillandsia pohliana, Tillandsia tricholepsis, and Tillandsia recurvata were collected from trees and fences on the campus of the Federal University of São Carlos (São Carlos, SP). The plants were properly disinfected for the isolation of bacteria of interest, with aliquots plated on Petri dishes containing 10% TSA and Casein Glycerol media, and incubated at 30°C for 30 days. Microorganisms were isolated in pure cultures, which were then subjected to tests for nitrogen fixation in NFb medium, inorganic phosphate solubilization in solid culture medium containing tricalcium phosphate, indole-3-acetic acid (IAA) production, and antimicrobial activity against medically relevant pathogens. From the seven plant samples collected, 54 bacterial isolates were obtained, of which 46% came from tree collections and the remainder from fences. Overall, 46% of the bacteria were positive for nitrogen fixation, 59% were capable of phosphate solubilization, and all of them produced IAA in vitro. One isolate exhibited antimicrobial activity against Staphylococcus aureus. Statistical analyses highlighted the efficiency of the ACG medium for bacterial isolation and revealed no significant differences in the mean values obtained from the assays regarding bromeliad species or collection site. These results demonstrate the high microbial diversity present on the leaf surfaces and within the tissues of bromeliads from the genus Tillandsia, indicating the crucial role of these isolates in plant nutrition and growth, and confirming their potential use as bioinoculants.